Improved morphology for ohmic contacts to AlGaN/GaN high electron mobility transistors using WSi[sub x]- or W-based metallization

Luo, B.; Ren, F.; Fitch, R. C.; Gillespie, J. K.; Jenkins, T.; Sewell, J.; Via, D.; Crespo, A.; Baca, A. G.; Briggs, R. D.; Gotthold, D.; Birkhahn, R.; Peres, B.; Pearton, S. J.
June 2003
Applied Physics Letters;6/2/2003, Vol. 82 Issue 22, p3910
Academic Journal
A comparison was made of specific contact resistivity and morphology of Ti/Al/Pt/WSi/Ti/Au and Ti/Al/Pt/W/Ti/Au ohmic contacts to AlGaN/GaN heterostructures relative to the standard Ti/Al/Pt/Au metallization. The W- and WSi-based contacts show comparable specific resistivities to that of the standard contact on similar layer structures, reaching minimum values of ∼10[sup -5] Ω cm[sup 2] after annealing in the range 850–900 °C. However, the W- and WSi-based contacts exhibit much smoother surface morphologies, even after 950 °C annealing. For example, the root-mean-square roughness of the Ti/Al/Pt/WSi/Ti/Au contact annealed at 950 °C was unchanged from the as-deposited values whereas the Ti/Al/Pt/Au contact shows significant deterioration of the morphology under these conditions. The improved thermal stability of the W- and WSi[sub x]-based contacts is important for maintaining edge acuity during high-temperature operation. © 2003 American Institute of Physics.


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